KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 423 



Description. — The body is asymmetrically subellipsoidal, flattened on the twisted ventral 

 face between pores, more convex dorsally, tapering somewhat posteriorly. The epicene is larger 

 than the hj'poeone, with the apex broadly rounded and antapex button-shaped, encircled dorsally 

 by the distal end of the sulcus. The anterior and posterior flagellar pores are located on opposite 

 faces due to the torsion of the body. 



The girdle forms a descending left spiral of 1.5 turns. Its proximal end is 0.35 of the total 

 length of the body from the anterior end and its distal end 0.16 from the posterior end. Its 

 total displacement measured in the anterojiosterior direction is 0.75-0.85 transdiameter or about 

 0.5 of the total length. The furrow is deeply impressed with prominent lips. The sulcus extends 

 from near the apex spirally in descending left spiral of 1.25 turns of a narrow groove. There 

 is only 0.5 Uirn in the intercingular region, the remaining 0.75 being mainly in a posterior curve 

 around the "dorsal" side beyond the emergence of the posterior flagellum. It is possible that 

 the dorsal part of this posterior region is not true sulcus. The posterior part of the sulcus lies 

 in a deep ventral depression at the right side of the ocellus. It is also possible that there is 

 more of an anterior loop than appears in the figures. The anterior and posterior flagellar pores 

 are at the anterior and posterior junctions of sulcus and girdle respectively. The transverse 

 flagellum traverses the whole length of the girdle. 



The ocellus is located far posterior, on the left side of the distal end of the sulcus, but still 

 mainly within the intercingular region of that gi'oove. This location appears more clearly in 

 the text figure than in the other figures (pi. 11, fig. 122, and text fig. NN, 2) from a slightly 

 difi'erent angle, owing largely to the deep ventral depression in which this part of the sulcus lies. 

 Tlie ocellus has a length of 0.5 transdiameter and its nmiu axis is almost horizontal and is 

 directed ventrally. It is of the simple type with a spherical lens of several concentric laminae 

 of equal thickness of a pale lemon-yellow color. One face is slightly covered by the irregularly 

 hemispherical black pigment mass, half again as large as the lens. A lighter core without 

 noticeable color lies in its center. 



The most noteworthy feature of this animal is its nematoeysts. These lie in a group of eight 

 to eleven clustered near the nucleus and are all directed more or less anterodorsally. They 

 are greenish peg-shaped bodies, faintly capitate, from 14—22/i in length and 3-4/a in greatest 

 diameter. Each shows within a faint coil, the introverted thread. The arrangement varies 

 somewhat in different individuals, but the general direction and location are similar in all. The 

 differences in size are similar to those found in Polykrikos, and seem to be correlated with 

 varying degrees of distinctness of the thread. This is an indication of stages in development 

 or age of these organs. There is no evidence in our material tliat they are derived from or 

 associated with an.y organism used as food, and they are not located in vacuoles. 



The nucleus is spheroidal, about 1.5 transdiameters in diameter and is located in the anterior 

 half of the body. As binary fission approaches it becomes obliquely elongated or reniform, and 

 lies with its long axis about 70° from the major axis. It is filled with fine, parallel, mouiliform, 

 chromatin threads which run spirally about the long axis. 



A small pusule was noted at the anterior flagellar pore, and in one individual a veiy large 

 posterior pusule extended from the posterior flagellar pore up to the nucleus. These pusules 

 are filled with a pinkish fluid. No food balls were seen. 



The color of this species has been found to be quite variable, possibly because of the results 

 of previous ingested food. Dogiel (1906) gives to his figure a pale ochraceous color, located in 

 ehromatophore-like bodies. One individual seen by us had more of an amber-yellow tone, due 

 also to chromatophore-like bodies distributed near the surface, principally dorsally, while in 

 another the protoplasm was lavender grey with no trace of yellow or chrotnatophores. Minute 

 glaucous green granules fill the periphery as cytoly.sis approaches. Dogiel figures lines of black 

 pigment granules in the lower part of the hypocone below the girdle arranged as if along striae, 

 though no such structural differentiations were to be detected in the surface plasma. In one 

 (as. only did we find a detached pigment granule, and this lay anterior to the proximal end of 

 the girdle. 



